1. Field of the Invention
The present invention relates to a motor including a brush, and particularly, to an equalizer structure.
2. Description of the Related Art
For example, an equalizer structure is disclosed in JP 2002-186210A. In JP 2002-186210A, the equalizer is wound around a slot of an armature core and connects commutator pieces having the same potential.
In recent years, advances have been made regarding the miniaturization of motors with brushes. In a small-sized motor with a brush, a concentrated winding structure capable of decreasing a height in an axial direction is used. However, in the concentrated winding structure, in general, there is a need for the number of the magnetic poles of magnets or the number of the brushes to be increased. Taking into consideration costs, sound characteristics, and the like, it is preferable that the number of the brushes is decreased. However, if the number of the brushes is decreased, the current capacity of the equalizer becomes a problem.
This is explained with reference to FIGS. 1A and 1B. In FIGS. 1A and 1B, the reference numeral 101 indicates brushes, 102 indicates segments, 103 indicates coils, and 104 indicates an equalizer. For example, as shown in FIG. 1A, in a case where the brushes 101 directly contact the segments 102 to which the coils 103 supplied with current are connected, even though a plurality of coils 103 is connected to the segments 102 in parallel, a current “i” can be supplied to each coil 103 without difficulty.
However, as shown in FIG. 1B, in a case where the equalizer 104 is used while the number of the brushes is decreased, the total capacity “2i” of the current to be supplied to each coil 103 flows through the equalizer. Thereby, if the current capacity of the equalizer 104 is insufficient, there is a concern that the equalizer 104 may be blown out. With respect to this concern, for example, the following two measures are considered.
(1) As the coils and the equalizer, different conducting wires are used, and diameter of the equalizer is greater than that of the coil.
(2) As the coils and the equalizer, the same conducting wire is used, and the diameter of the equalizer and the diameter of the coils are greater.
However, in measure (1), the connection operation between the coils and the equalizer is increased, whereby there are problems in that an increase in the costs or a decrease in the productivity occurs. In measure (2), a winding process becomes difficult if the diameter of the conducting wire of the coil is increased, and there is a problem in that a decrease in the productivity occurs.
Thus, as a measure to attempt to solve the problems, it is considered that a plurality of lines of equalizers is made. Regarding this measure, in paragraph [0031] of JP 2000-060074A, a structure is disclosed in which two points of segments having the same potential are connected by a plurality of equalizers. Moreover, also in paragraph [0012] of JP 2002-186210A, a structure is disclosed in which two equalizers are wound around between commutator pieces.
However, as in JP 2002-186210A or JP 2000-060074A, if the segments having the same potential are connected by the plurality of equalizers, a loop circuit is formed between the equalizers. In addition, if the equalizers are wound around an armature core, an induced voltage is generated in the equalizers.
If the induced voltage is generated in the equalizers, circulating short-circuit current is generated in the loop circuit, and a decrease in motor efficiency occurs.